Rocker lever assemblies are used in internal combustion engines to control the opening and closing of intake and exhaust valves. An example of such a rocker lever system is generally disclosed in U.S. Pat. No. 5,636,600, assigned to Cummins Engine company, Inc. Rocker lever assemblies typically include a rocker lever with first and second lever arms that are pivotable about a pivot axis. The end of the lever arm engages the valve cross head of one or more intake or exhaust valves. During the downward pivoting movement of the lever arm, the lever arm pushes the valve crosshead and therefore the valve linearly downward to open the valve. During upward pivoting movement of the lever arm, a spring urges the crosshead upward against the lever arm to close the valve.
Translating the partial rotary path of the rocker lever into linear reciprocation of the valves causes a transverse sliding movement between the valve crosshead and the end of the lever arm. Accordingly, a tappet assembly, also commonly known as an "elephant's foot", is employed to drivingly connect the lever arm to the valve crosshead to facilitate reciprocating linear movement of the valve while allowing for transverse sliding movement between the valve crosshead and the end portion of the lever arm. Various attempts at tappet assemblies or other related ball and socket joints for rocker lever assemblies and other lever assemblies are generally disclosed in U.S. Pat. Nos. 1,958,264, 1,699,657, 1,504,496, 1,521,623, 1,515,201, 3,016,887, 4,905,577.
A common way of providing a tappet assembly has been to provide a threaded screw shaft having a hemispherical ball end in combination with a tappet socket. The tappet socket typically includes spherical recess receiving the ball end and a flat engaging face for engaging a corresponding flat face of the valve crosshead. From a standpoint of initial assembly of the rocker lever assembly, and disassembly and reassembly of the rocker lever assembly for repairs, it is highly desirable that the tappet socket, which is typically relatively small, be retained to a larger component to prevent the tappet socket from falling out or becoming misplaced. It is also a requirement in some applications that the tappet assembly must provide enough room to set the lash in the system.
Attempts to retain the tappet socket include connecting the tappet socket to the threaded fastener (that has a ball-end) with a flexible connector or deforming an outer edge of the socket around the ball end of the fastener. However, these attempts are economically disadvantageous from both a parts cost and an assembly/manufacturing cost. Some of these prior attempts have also had reliability drawbacks or used undesirably excessive space.